Thermostatic electric switch and contact structure therefor



My 18, 1937. J, D BQLESKY Y 2,080,556

THERMOSTATIC ELECTRIC SWITCH AND CONTACT STRUCTURE THEREFOR Filed Nov. 22, 1.935-

/ 7 l 4 :K M /0 aan Patented May 18, 1937 PML-:NTl oFFlcE THERMOSTATIC ELECTRIC SWITCH AND CONTACT STRUCTURE THEREFOR John D. Bolesky, Attleboro, Mass., assignor, by mesne assignments, to Metals & Controls Corporation, Attleboro, Mass., a corporation of .l Massaal:

nsetts Application November 22, 1935, Serial No. 51,034

4 Claims. This invention relates to thermostatic-*electric switches and contact structures therefor, andl the provision of a switch and contact structure therefor, wherein provision is made for more rapidly cooling the contacting elements of the heat generated therein by the making and breaking of circuits therewith; and the provision of a switch and contact structure' of the class de.

scribed which is relatively simple and economical to manufacture. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the kelements and combinations of elements, features of construction, and arrangementsof parts `which will be exemplified in the structures hereinafter described, and the scope of-l the application of which will be indicated in the following claims.

In the accompanying drawing, in which are illustrated several of various possible embodiments lci'` the invention,

Fig. 1 is a plan view, partially broken away, of a thermostatic electric switch embodying the present invention;

Fig. 2 is a plan view of one form of contact element;

Fig. 3 is an end elevation of the contact element of Fig. 2; a

Fig. 4 is a side elevation of the contact element of Fia. 2';

Fig. 5 is a plan view of a second contact element;

Fig. 6 is an-end elevation of the contact element of Fig. 5;

Fig. 7 is a cross section taken substantially along line I-1 of Fig. 1, and illustrating the switch in closed position; and,

Fig. 8 is a cross section similar to Fig. '1,' illustrating the switch in open position.

Similar reference characters indicate corresponding parts throughout the several views `of the drawing.

This invention is in thenature of an improvement on the thermostatic electric switch, and the contacts embodied therein, as shown in L. K. Marshall Patent 1,700,172, dated January 29, 1929.

The general association oi elements Is quite similar to that of the said Marshall patent, the

improvement lying more particularly in the particular contact structure provided in the present invention.

Referring now more particularly to Fig. 1, numeral I indicates a base portion comprising a substantially circular metal member upon which is positioned a circular disc 2 oi a suitable insulatingmaterial, such as mica. A plurality of contact members 3, l, 5, and 6, which are described in greater detail hereinafter, are held in the uppersurface of the insulating disc 2 by suitable means, such as rivets 1 and 8.

Numeral 9 indicates athermostatic disc which is of the type disclosed in Spencer Patent 1,448,240, dated March 13, 1923. The disc 9 is supported on the circular base plate I by means ofv-a stud l (see also Fig. 7) threadedtherein. On the stud I0 are threaded, rst, a collar II having an outwardly extending flange I2, and

second, a nut I3. A central hole or opening M in the disc 9 nts on the collar II and is held in position between the ilange I2 and the lower face of nut I3., 'I'he arrangement is such that the disc is firmly held but permitted 'suillcient play to permit it to snap between its opposite positions oi concavity in response to ambient temperature changes.

Also threaded into the b ase I are one or more pillars or posts I5, which extend upwardlythrough suitable openings I3 in the disc 8. The engagement of t posts I and openings I6 prevent the disc 9 from rotating on the stud III relative vto the base I.

A plurality of contact bridging members I1 are secured to the thermostatic disc in spaced positions adjacent to the periphery thereof in such positions that they will operatively engage the adjacent end portions of pairs of the respective fixed contact members 3, 4, 5, and 6, respectively. Since the particular structure of the movable contacts I1 form no part of the present invention,'they will be described only generally. Numeral I8 indicates a rivet which passes through the disc 8. It is insulated from the disc 3 by mica washers I9. Numeral 20 indicates a washer formed with a spherical surface 2|, which is secured on the rivet I8 on the under side of the disc 9. At the lower end of the rivet I8, there is loosely held a disc 22 of good contact metal, such as silver.

. It is with the construction of the xed contact members 3, I, 5, and 8 that the present invention is most particularly concerned. In prior switches of this general type, such as that shownin the aforesaid Marshall patent, the analogous fixed contact members were stamped from flat sheets of metal and had no projections extending out from their flatness. This meant thatthey laid fiat against the base member I in assembly. Their respective ends which constitute the active contact-engaging faces for the movable contacts I1, were thus positioned at such an angle with respect to the movable contact member 22 that there was, particularly during the switch opening operation, a tendency for the movable contacts 22 to lift first from one side of the fixed contacts only to achieve a complete separation by lifting the other side. This sequence was not such as to produce the most advantageous form of break between the contacts; in certain instances, regardless of the speed with which the movable contact 22 was moved, there was a tendency, due to the irregular manner in which the movable contact separated from the fixed contact, to cause arcing, whereby the contacts, both fixed and movable, were unduly heated and corroded.

The difficulty with such completely fiat, fixed contacts is solved in the present invention by providing the fixed contact pieces 3, 4, 5, and 6, and more particularly their contact-engaging ends, with faces or portions that are upset or stamped fromthe main fiat plane of the contact. This arrangement is indicated in Figures 2, 3 and 4, with respect to the fixed contact elements 3 and 4 which are relatively long and have contact engaging faces on each end thereof. Referring to l Fig. 2, numeral 23 designatesthe so-shaped contact engaging end portions. Figures 3 and 4 show how these are formed from the main body of the contact 4. The contact v4 may be considered, roughly, as a peripheral segment of a circle or an annular segment. .The contact-engaging ends 23 are so formed as to slope upwardly and outwardly, away from the assumed center of the segment. Considered in another light, the main body of the contact 3 is a portion of a fiat disc while the ends 23 are portions of a cone or sphere having its center on the same line as the center of the disc.

While the contact portion 3 has been referred to as fiat, by reference to Fig. 4, it will be seen that it is in reality slightly arched. This slight arching is for the purpose of more eiIectively securing the contact member 4 to the base plate I, by providing tension in the rivets 1. When the contact element 3 is removed from the base I it has the said slight arching, but when it is mounted on the base I, it is flattened out into a completely flat position.

Contact members 5 and 6 which constitute the terminal pieces of the switch, are short pieces relative to contact members 3 and 4. They are illustrated more particularly in Figs. 5 and 6. They have contact engaging faces 23 on but one end thereof, but these faces 23 are sloped in the same manner as the faces of the contact members 3 and 4.

In the case of the contact' members 3 and 4,

. two rivets 1 are provided for each such contact member. 'I'his means that there can be no doubt of their proper angular positioning on the base plate I. However, in the case of the contact members 5 and 6, there is but one rivet l provided, and in order to make sure that the angular position of the contact members 5 and 6 is correct, the rivets 8 therefor are of polygonal (hexagonal. for example) cross section. A correspondingly polygn onal opening 25 is formed in each of the contact members 5 and 6. The opening 26 (see Fig. 7) in the base plate I is likewise polygonal so that when the polygonal rivet 8 is used to secure the contact elements 5 and 6 to the base plate I, there is no doubt of their correct angular positioning.

The manner in which the sloping faces 23 of the fixed. contact members of the present invention are more advantageous is indicated in Figures 1 and 8. In Figure 8, for example, the switch is in open position. It will be seen that the movable contact button 22 naturally assumes a position which is almost exactly parallel to the position of the sloping faces 23 of the fixed contacts. When the disc 9 snaps to the circuit-closed position, the inertia of the button 22 is such that it is'maintained in substantially the same position shown in Figure 8 even though that involves an angular shifting of the position of the rivet I8 with respect to the button 22. This means that the movable contact button 22 and the fixed contact 23 are brought together in parallel relationship and touch each other over the entire engaging surfaces at practically the identical instant. Figure 7 shows the contact-closed position.

On the other hand, when the disc 9 snaps back from the Fig. '7 to the Fig. 8 position, opening the circuit, the same condition prevails and vinertia holds the movable contact button 22 in substantially the same angular position. Thus, the button 22 moves away from the fixed contact 23 maintaining its parallel relation thereto, and a complete and uniform separation is obtained over the entire contact area at the same instant.

These advantageous conditions in the making and breaking operations are not to be obtained with the completely flat fixed contacts of the aforesaid Marshall patent structure, for example.

Another considerable advantage of the xed contact structure of the present invention is that the contacting regions or surfaces 23 are all displaced to a small, but measurable extent from the surfaces of the mica disc 2. yThis leaves a space which is indicated in Figure 7 for example, by numeral 21. Into this space 21, the ambient medium such as air, may readily circulate. This circulation of air aids in effecting a quick cooling of the contact surfaces if they have become heated. In other words, the fixed contact of the present invention provides for the circulation of air therearound and thus can cool off much more quickly than the fixed contacts of the aforesaid Marshall structure, for example, where the air can effectively reach only one surface (the upper surface) of the fixed contact. This cooling etiect is of course advantageous.

n In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in carrying out Vthe above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. In a thermostatic electric switch, a base member, a snap acting thermostatic disc mounted thereon at its center, said snap acting disc carrying at least one movable contact member at its periphery, and at least one fixed contact member mounted on said base in position to cooperate with said movable contact member, said fixed contact member having a contact engaging face sloped at an angle to the surface of the base member, said sloped portion sloping away from the point of mounting oflaid disc thereon at its center, saidsnap acting disc carrying a pluralityof movable contact members' at its periphery, andra plurality of fixed contact members mountedonsaid lbase in position to cooperate with said movable contact members, said fixed contact membersL having a contact en gag`ing face substantially conforming to an imaginary cone surface theapex of which is in line with the point of mounting of said disc.

3. A xed contact member forswitches of theI classdescribed comprising a substantially flat piece roughly shaped as a segment of im annulus.

at least one end-of said piece being provided with aface sloping with respect to the surface of the remainder of the piece, said sloping face sloping away from the center of the annulus of which the contact is a segment.

. remainder ofthe piece. saidl sloping face sloping ina direction upwardly and away from the center of the annulus of which the contact is a segment.

JOHN D. BOLESKY. 

